1. Field of the Invention
The present invention relates to microcapsules containing a hydrophobic, volatile substance as a core substance and a process for producing the same.
2. Discussion of the Background
Microencapsulation of perfumes, agricultural chemicals, adhesive agents and the like which contain hydrophobic, volatile substance(s), for instance, a fraction boiling at a low temperature has been demanded from the viewpoints of preventing the volatilization of the volatile substance as an active ingredient during preservation of the perfumes, agricultural chemicals, component(s) of adhesive agent and the like.
Although there are various proposed methods for microcapsulating the hydrophobic, organic compounds hitherto (for instance, refer of Japanese Patent Publication No. 771/1967), since it is impossible in the conventional methods to form a wall membrane of the microcapsules, which is completely dense and compact, the maintenance of the core substance in the microcapsules is insufficient. Accordingly, in the case of subjecting a volatile substance to microencapsulation as the core substance, the loss of the volatile substance is large due to evaporation in the step of microcapsulation and the step of drying the wet microcapsules. As a result the reduction of the yield of microcapsulation is caused, and in addition, the evaporation of the volatile substance causes the formation of micro-pores in the wall membrane of the microcapsules, thereby inducing the large defect of remarkably reducing the heat-resistance and solvent-resistance of the thus obtained microcapsules.
A process for microcapsulation by interfacial polymerization of a polyvalent isocyanate with water or a polyvalent amine has been known(refer of Japanese Patent Publication No. 771/1967). However, since the wall membrane of the microcapsules, which is formed by interfacial polymerization is a single membrane consisting of polyurea and it is impossible to obtain the membrane provided with a sufficiently compact and dense structure, it is inevitable that the capability of the wall membrane in retaining a volatile substance as the core substance within the microcapsules is very poor. Accordingly, the process is poor in practicality for microcapsulating a volatile substance.
The present invention provides microcapsules from which the volatile substance as the core substance does not dissipate during the steps of microcapsulation and drying by microcapsulating the hydrophobic, volatile substance, particularly the organic compound with a completely compact and dense wall membrane. The other objects will become clear from the following description.